• Journal of Microbiology and Biotechnology
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• v.33 no.8
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• pp.1023-1029
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• 2023

Biosurfactants reduce surface and interfacial tension due to their amphiphilic properties and are an eco-friendly alternative for chemical surfactants. In this study, a new yeast strain JAF-11 that produces a biosurfactant was selected using drop collapse method, and the properties of the extracts were investigated. The nucleotide sequences of the strain were compared with closely related strains and identified based on the D1/D2 domain of the large subunit ribosomal DNA (LSU) and internal transcribed spacer (ITS) regions. Neodothiora populina CPC 39399^T, the closest species with strain JAF-11, showed a sequence similarity of 97.75% for LSU and 94.27% for ITS, respectively. The result suggests that the strain JAF-11 represents a distinct species that cannot be assigned to any existing genus or species in the family Dothideaceae. Strain JAF-11 produced a biosurfactant reducing the surface tension of water from 72 mN/m to 34.5 mN/m on the sixth day of culture and the result of measuring the critical micelle concentration (CMC) by extracting the crude biosurfactant was found to be 24 mg/l. The molecular weight 502 of the purified biosurfactant was confirmed by measuring the fast atom bombardment mass spectrum. The chemical structure was analyzed by measuring ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and two-dimensional NMRs of the compound. The molecular formula was C₂₆H₄₆O₉, and it was composed of one octanoyl group and two hexanoyl groups to myo-inositol moiety. The new biosurfactant is the first report of a compound produced by a new yeast strain, JAF-11.

• Korean Journal of Culture and Social Issue
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• v.10 no.3
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• pp.83-101
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• 2004

This study investigated the effects of social presence as means of self-awareness and interpersonal-awareness on the cyber-aggressive behavior. The cyber-aggressive behavior (flaming and direct aggression use of character) should be differ from existence of social presence and type of social presence of internet users. To test hypothesis, an experiment was executed a field study on cyberspace, an on-line game, "fortress 2 blue forever". I made a chat-room in the game site to conduct an experiment to 107 person who entered the chat-room and blinded ignorance of this situation made by researchers. As the subjects enter the chat-room, he chats with 3 researchers who were waiting before he gets in. The social presence was operated with 3 phases by the contents of the chat (①control group; nothing, ②experimental group 1; reaction about other people ③experimental group 2; reaction about other people + self-exposure by an exchange information of their home region). The studies show that, subjects of the control group behaved more aggressively than other subjects of the experimental groups(both flaming and direct aggression use of character). Meantime, I compared experimental group 1 with experimental group 2 to investigate difference between the type of social presence. As the result, subjects of the experimental group 1 behaved more aggressively than experimental group 2 (only flaming, there's no difference in direct aggression use of character).

• Journal of the Korean Society of Food Culture
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• v.7 no.4
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• pp.329-338
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• 1992

This study was attempted aimed to prepare of Andong sikhe by pure culture inoculation and to improve storage stability by the addition of stabilizers to the product. Lactobacillus delbreuckii was selected for pure culture inoculation in the fermentation. The effect of stabilizers on the sedimentation, sensory evaluation and viscosity of Sikhe were investigated during the fermentation of traditional Andong Sikhe stored at $4^{\circ}C$ Morphological characteristics of Sikhe were determined by scanning electromicrograpy. Among the stabilizers added to the traditional Andong sikhe Na-alginate was found to be best stabilizers. When the product was evaluated by the sensory panel, the addition of stabilizers up to 0.1% level actually increased the acceptability of the product, while the concentration of more than 0.2% stabilizers affected the acceptability of the negatively. Sikhe added Na-carboxymethyl cellulose and Na-alginate showed highest viscosity on the 2nd day of fermentation, while homogenized Andong sikhe with Carrageenan showed the highest peak in viscosity on the first day of fermentation. Lactic acid bacterial count reached to $3.2{\times}10^8/ml$ after 20 days of storage. The surface and cross section of rice was observed by scanning electron microscope. As the fermentation proceeded holes on the surface increased, and nearly empty cell wall remained at the later stage of fermentation. Use of pure cultured inoculum of L. delbreuckii supported the rapid build up of the lactic acid bacteria and consequently the whole process of the fermentation was shortened. The acceptability and product quality were improved by use of L. delbreuckii inoculum.

• KSBB Journal
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• v.15 no.2
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• pp.167-173
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• 2000

For selective elimination of salt from boiled oyster extract (BOE), electrodialyzer was used and the desalination conditions of B BOE were investigated. The ion-exchange membrane with a molecular weight cut off 100 Da was used for desalting of B BOE. The desalination efficiency at pH 4.0 was 13% higher than that at pH 9.0 when BOE was desalted for 90min. The e electrodialysis pro$\infty$ss could remove above 90% of the initial salt content when 5% BOE was desalted at pH 5.62 for 1 100min. The initial volume and concentration of permeation solution did not have significant effects on desalination time and r ratio. The important factors for the desalination of BOE were found to be pH and concentration of BOE. The results obtained prove that electrodialysis is a practical solution to the problem of selective elimination of salt from BOE.

• Economic and Environmental Geology
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• v.36 no.5
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• pp.375-380
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• 2003

This study was carried out 1) to investigate the pH effect on solubilization of phenanthrene by biosurfactant in aqueous system and 2) to evaluate the pH effect on the biodegradation rate of phenanthrene in the presence and the absence of the biosurfactant by phenanthrene degraders. Tween 80, which is a chemically synthesized surfactant, showed greater solubilizing capacity than rhamnolipid. The solubilization capacity can be expressed as a MSR(molar solubilization ratio=moles of organic compounds solubilized per mole of surfactant). The calculated MSR of Tween 80 and rhamnolipid were 0.1449 and 0.0425 respectively. The kinetic study of phenanthrene solubilization by rhamnolipid showed that solubilization mechanism could reach equilibrium within 24 hours. Addition of 240 ppm rhamnolipid solution, which concentration is 4.3 times of Critical Micelle Concentration(CMC), caused 9 times solubility enhancement compared to water solubility. The highest solubilities were detected around a pH range of 4.5-5.5. Changes in apparent solubility with the changes in pH are possibly related to the fact that the rhamnolipid, an anionic surfactant, can form different structures depending on the pH. Two biodegradation experiments were performed in the absence and the presence of rhamnolipid, with the cell growth investigated using a spread plate method. The specific growth rates at pH 6 and 7 were higher than at the other pH, and the HPLC analysis data, for the total phenanthrene loss, confirmed the trends in the $\mu$(specific growth rate) values. In presence of rhamnolipid, maximum $\mu$ values shifted from around pH 5 which showed maximum enhancement of solubility in the abiotic experiment, compared to the $\mu$ values obtained without the biosurfactant. In this study, the increase in the observed specific grow rate(1.44 times) was not as high as the increase in solubilization(5 times). This was supported by the fact all the solubilized phenanthrene is not bioavailable to microorganisms.

• Microbiology and Biotechnology Letters
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• v.15 no.6
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• pp.388-395
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• 1987

In order to obtain a regulatory mutant strain with high cellulase activity, a newly isolated Penicillium verrculosum, strain F-3 was used as parental strain since it was proved to be an efficient cellulase producer. A number of experiments were conducted to determine the optimum conditions to in-duce mutagenesis and isolate the desirable mutant strains. Out of several restriction compounds tested, 1.5% oxgall was found to be most effective to restrict the colony size by suppressing overgrowth. Derepression of catabolites was employed as a criterion in selecting mutant strains with high cellulase productivity. Production of cellulase by Penicillium venculosum F-3 was suppressed when cultured on the media with more than 1% of glucose or glycerol. It was found that either irradiation with UV light for 19 mins or treatment with nitrosoguanidine at 200$\mu\textrm{g}$/m1 for 60 mins, induced mutagenesis at desired level, when the survival rate of the spore was 0.2% and 48%, respectively. Three mutant strains of F-3, UV-9, UV-10, and NTG-3 that had the highest cellulase productivity were finally selected, based on filter paper degradation rate, size of clearing zone on the screening plate and cellulase activity in the medium containing cellulose powder. When the mutant strains were compared with parental strain F-3, on the KC-M-W medium containing cellulose powder, the filter paper activities of UV-9, UV-10, and NTG-3 were increased by 34%, 55%, and 41%, respectively. However, the assimilation of cellobiose octaacetate by UV-9 or NTG-3 was markedly reduced. When the mutant UV-10 was grown on cellobiose octaacetate medium (CCA-4) in shaking flasks, the cellulase activities of the mutant increased by 20 to 50% compared to the parental strain. Excreation of soluble protein from the mutant also elevated up to 30%. The mutant also constitutively produced both CMCase and $\beta$-glucosidase, though at relatively low level, in the presence of glucose or cellobiose as carbon sources.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.6
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• pp.432-445
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• 2000

The objective of this study was to determine the effects of various kinds of composts on the change of nutrition loss in upland soils. Field experiments were conducted in the loam and sandy loam soils, while the clay loam and sandy loam soils were used for laboratory experiments. Various kinds of composts such as poultry manure compost(PMC), cow manure compost(CMC), human excrement sludge(HES), and food industrial sludge compost(FISC) were applied annually at rates of 0, 40, and $80mg\;ha^{-1}$ to soils grown with soybean and maize plants for 4 years during 1994 to 1997. The results of this study were as follows : The loss of nutrients in the form of cation and anion by run-off water increased with the increase of compost application rate. Compared with bare soils, maize cultivation decreased the nutrient loss by run-off from soils by 43% in anionic form and 32% in cationic form. Amount of cation loss were ordered $K^+$ > $Ca^{2+}$ > $Na^+$ > $Mg^{2+}$ > $NH_4{^+} $ and that of anion loss were ordered $SO_4{^{2-}}$ > $NO_3{^-}$ > $Cl^-$ > $PO_4{^{3-}}$. Nutrient loss of sand loam soil in the cation and anion by percolation water increased 1.7 times compared with loam soil. $NO_3{^-}-N$ contents in percolated water were high at the initial stage after compost application, and the amounts were higher in sandy loam soil than loam soil. The maize cultivation also decreased the $NO_3{^-}-N$ contents in percolated water by 82% in loam soil, and 58% in sand loam soil. Soil pH of composts determined by laboratory incubation test increased pH 6.1~6.8 application with poultry and cow manure compost but application with human excrement sludge decreased pH 4.5~4.7. Soil EC were increased initially composts application and decreased up to 2 weeks, thereafter kept a certain level. Nitrogen mineralization rates of composts determined by laboratory incubation test at $25^{\circ}C$ were 39~76% in sandy loam soil, and 16~48% in clay loam soil.

• The Korean Journal of Mycology
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• v.13 no.3
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• pp.157-168
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• 1985

To investigate nutritive values of a feed fermented with basidiomycetes, among the isolated strains, Lyophyllum decastes (Fr.) Sing. was found with the greatest enzyme productivity and rapid mycelial growth in rice straw medium. Optimum temperature, pH and moisture content for mycelial growth and enzyme production of the strain were $25{\sim}30^{\circ}C,\;pH\;4.0{\sim}7.0\;and\;70{\sim}75\;%$, respectively. Fifteen days of culture were required for the highest enzyme productivity. Among the sub-materials added, $30{\sim}40\;%$ of rice bran and $10{\sim}20\;%$ of defatted perilla seeds were effective for the enzyme production, but caused a reduced mycelial growth. The greatest effect of an addition of inorganic salts was obtained with $0.36{\sim}0.72\;%\;of\;(NH_4)_2HPO_4$. When 40 mesh or smaller rice straw and steam treatment at $0.5\;kg/cm^2$ were used, the mycelial growth decreased, whereas the enzyme production increased. The mycelial growth and enzyme production increased when $Ca(OH)_2$ was used as the alkali treatment, but decreased with increasing concentration of NaOH. As the fermentation proceeded, the amounts of ash, reducing sugar and total nitrogen increased, but cellulose, lignin and pentosan decreased. When the rice straw was treated with alkali, the amounts of ash, total nitrogen and lignin decreased, but reducing sugar and cellulose increased. At higher NaOH concentration, the variation become greater. The in vitro dry matter digestibility of the products increased from 55.03 % at the beginning of the fermentation to 62.72 % at 45 days after fermentation. The most effective alkali treatment on the digestibility of rice straw was KOH followed by NaOH. However, the digestibility increased with increasing concentration of NaOH. The digestibility of pretreated with alkali increased after fermentation as well.

• Applied Biological Chemistry
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• v.45 no.2
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• pp.71-76
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• 2002

Several antagonistic bacteria, SD-1, 4, 10, 11, 14, 15, and 16, which have strong CMCase and amylase activities, were isolated from the fermented mushroom media. Among them, SD-1, 10, 11, and 15 have strong antibacterial activities against the mushroom pathogenic bacteria Pseudomonas sp., and SD-1, 10, 11, 14, and 16 have strong antifungal activities against the mushroom pathogenic fungi, Trichoderma sp. SD-14, 15, and 16 did not inhibit the growth of mushroom Pleurotus eryngii ASI-2302, and Pleurotus ostreatus ASI-2042 and ASI-2180. When the culture broth mixture of the seven bacterial strains was applied to the mushroom media, the growths of pathogens, Pseudomonas sp. and Trichoderma sp., were inhibited.

• Korean Journal of Food Science and Technology
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• v.3 no.3
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• pp.178-184
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• 1971

Samples of refined soybean oil were irradiated with lights from a 20-watt incandescent tungsten lamp, a 20-watt fluorescent daylight type lamp, a 20-watt low-pressure mercury vapor germicidal lamp, and direct sunlight for an experimental period of 147 days. Some samples were stored in a dark room throughout the period as a control. The peroxide values of all samples were measured every week. The induction period of the samples was arbitrarily taken as the time required for the samples to reach a peroxide value of 15. The induction period of the control was estimated at 198 days. Those of the samples irradiated with the incandescent light, the fluorescent light, the ultraviolet light, and the sunlight were estimated at 196, 119, 52 and 6 days, respectively. The sunlight showed by far the strongest prooxidant activity whereas the incandescent light showed the weakest but distinct prooxidant activity. The small temperature differences observed among the various samples throughout the experimental period did not seem to affect the oxidation rates of the irradiated samples in any significant way.